NATIONAL OPEN UNIVERSITY OF NIGERIA

UNIVERSITY VILLAGE, PLOT 91, CASDASTRAL ZONE, NNAMDI AZIKIWE EXPRESS WAY, JABI, ABUJA.
FACULTY OF SCIENCES
JANUARY/FEBRUARY 2018 EXAMINATION

Course: CIT 445 – Principles and Techniques of Compilers

Time Allowed: 3 Hours

Instructions: Answer Question 1 and three (4) other questions

Q1       a. Define the following terms.

1. Formal grammar                                                                    (2 marks)
2. Parsing                                                                                                (2 marks)
3. Strings                                                                                     (2 marks)

b. Enumerate three components that make up the syntax of grammars     (6 marks)

            c. List two types of grammars.    (2 marks)

Q2       a. Given the grammar G with following production rules, S → a | aS | bS, determine whether the following strings can be generated by the grammar.

1. babaab 
2.  aaabbbab 
3.  bbaaba    (4 marks)

            b. With the aid of a diagram describe the levels of grammar as described by the Chomsky hierarchy.  (8 marks)

            c. Explain one of the uses of formal languages.   (2 marks)

Q3.      a. In the context of formal language describe the following terms.

1. Alphabet
2. Word
3. Letters                                                                                           (6 marks)

            b. Define format Languages.                                                                          (4 marks)

            c. What is the relationship between grammar and language.                      (4 marks)

Q4.       a. Define the term compiler and state its importance in the programming world.   (4 marks)

            b. Distinguish between a translator, compiler and an interpreter.               (6marks)

            c. Outline some specific knowledge require for building a compiler.           (4 marks)

Q5.      a. List and explain any three (3) components of a compiler.                         (6 marks)

            b. Explain why the error handler is important in a compiler.                                   (4 marks)

            c. Enumerate the functions performed by the lexical analyser.                    (4 marks)        

Q6.       a. Define context-free grammars (CFGs).                                                     (4 marks)

            b. Explain the role of the parser in (CFGs).                                                    (4 marks)

            c. Discuss the concept of parse tress.                                                             (6 marks)

Q7.       a. Briefly itemise and describe the different stages at which errors might occur during compilation.  (4 marks)

            b. Outline the different ways that error of division by 0 can be reported.   (4 marks)

            c. Distinguish between run-time errors and compile time errors.                (4 marks)

            d. Briefly describe some ways to check for ‘undefined.                                (2 marks)